We present results of a combined X-ray/optical analysis of the dynamics of the massive cluster MACS J0358.8–2955 ( z = 0.428 ) based on observations with the Chandra X-ray Observatory , the Hubble Space Telescope , and the Keck-I telescope on Mauna Kea .
MACS J0358.8–2955 is found to be one of the most X-ray luminous clusters known at z { > } 0.3 , featuring L _ { X, \mathrm { bol } } ( < r _ { 500 } ) = 4.24 \times 10 ^ { 45 } erg s ^ { -1 } , kT = 9.55 ^ { +0.58 } _ { -0.37 } keV , M ^ { 3 D } _ { gas } ( < r _ { 500 } ) = ( 9.18 \pm 1.45 ) \times 10 ^ { 13 } M _ { \odot } , and M ^ { 3 D } _ { tot } ( < r _ { 500 } ) = ( 1.12 \pm 0.18 ) \times 10 ^ { 15 } M _ { \odot } .
The system ’ s high velocity dispersion of 1440 ^ { +130 } _ { -110 } ~ { } km~ { } s ^ { -1 } ( 890 km s ^ { -1 } when the correct relativistic equation is used ) , however , is inflated by infall along the line of sight , as the result of a complex merger of at least three sub-clusters .
One collision proceeds close to head-on , while the second features a significant impact parameter .
The temperature variations in the intra-cluster gas , two tentative cold fronts , the radial velocities measured for cluster galaxies , and the small offsets between collisional and non-collisional cluster components all suggest that both merger events are observed close to core passage and along axes that are greatly inclined with respect to the plane of the sky .
A strong-lensing analysis of the system anchored upon three triple-image systems ( two of which have spectroscopic redshifts ) yields independent constraints on the mass distribution .
For a gas fraction of 8.2 % , the resulting strong-lensing mass profile is in good agreement with our X-ray estimates , and the details of the mass distribution are fully consistent with our interpretation of the three-dimensional merger history of this complex system .

Underlining yet again the power of X-ray selection , our analysis also resolves earlier confusion about the contribution of the partly superimposed foreground cluster A 3192 ( z { = } 0.168 ) .
Based on very faint X-ray emission detected by our Chandra observation and 16 concordant redshifts we identify A 3192 as two groups of galaxies , separated by 700 kpc in the plane of the sky .
The X-ray luminosity and mass of the two components of A 3192 combined are less than 0.5 % and less than 8 % of that of MACS J0358.8–2955 .